Neuro Flashcards
Final
What is the synaptic transmission?
the process by which impulses are communicated between neurons.
What type of sensory stimulus do free nerve endings receive (4)?
Free nerve endings receive various sensory stimuli such as touch, temperature, pain, and proprioception.
What types of input does the somatosensory system provide?
touch, temperature, proprioception, and pain.
What does “selective blockade” refer to in the context of the somatosensory system
ability to block specific types of sensory input based on type, location, or density.
How is sensory input converted to an impulse?
the process of transduction by sensory receptors.
How is the impulse conducted to the CNS
synaptic transmission
: What role do neurotransmitters play in synaptic transmission?
A: Neurotransmitters are the mechanisms by which impulses travel through the brain and between sensory and motor pathways.
How does chronic pain affect the threshold for action potentials?
Chronic pain causes depolarization, which narrows the gap between resting potential and threshold potential, making it easier to create an action potential with minimal stimulation.
What is a dendrite and what is its primary function?
A dendrite is a branched extension of a neuron that receives and transmits electrical impulses from other neurons or sensory stimuli to the neuron’s cell body.
How do dendrites contribute to the processing of signals in a neuron?
Dendrites receive incoming signals, including neurotransmitters and sensory stimuli, and transmit these signals to the neuron’s cell body, where they are processed and potentially generate an action potential.
Why are the structural features of dendrites important for their function?
branched structure and numerous dendritic spines of dendrites increase their surface area, allowing them to receive and integrate a large number of signals from other neurons or sensory inputs.
How does an impulse travel from the dendrite to the axon terminal?
An impulse travels from the dendrite to the nucleus, then to the axon hillock, and through the axon, which is surrounded by the myelin sheath.
What types of sensory input do dendrites receive?
Dendrites receive sensory input such as touch, pressure, substance P, and prostaglandins.
What happens to an impulse once it reaches the cell body?
continue as an action potential or stop at this point.
What is synaptic transmission? and 2 types
Synaptic transmission is a method by which cells communicate with other cells, either chemically or electrically.
What are the two types of synaptic transmission and how do they differ?
Synaptic transmission can be electrical, mediated through direct gap junctions, or chemical, where the gap junctions have no direct connection and involve neurotransmitter release.
What occurs during the chemical synaptic transmission process when an action potential reaches the presynaptic terminal?
Depolarization of the presynaptic terminal causes voltage-sensitive Ca++ channels to open, allowing Ca++ to enter the cell and stimulate exocytosis of neurotransmitter vesicles into the synaptic cleft.
What are the four key processes of synaptic transmission, and how can they be targeted for pain management?
Release of neurotransmitter: Can be stopped to block transmission.
Diffusion of neurotransmitter: A passive process; cannot be stopped.
Binding to post-synaptic receptors: Can be targeted by blocking receptors.
Inactivation of neurotransmitter: Can be blocked or modified through re-uptake or inactivation mechanisms.
What is the effect of excitatory synapses on the probability of action potentials in the post-synaptic cell
A: Excitatory synapses increase the probability of action potentials by raising the voltage of the post-synaptic membrane and bringing it closer to the action potential threshold.
What is the effect of inhibitory synapses on the post-synaptic cell?
reduce the probability of action potentials by decreasing or hyperpolarizing the membrane potential of the post-synaptic cell.
At what membrane potential is an action potential typically triggered?
-40 mV.
How does depolarization affect the release of neurotransmitters?
Depolarization increases the flow of Ca++ into the presynaptic terminal, which enhances neurotransmitter release. A longer action potential duration results in more Ca++ influx, and increased extracellular Mg++ can reduce neurotransmitter release by competing with Ca++.
What causes synaptic delay in neurotransmission?
caused by the time needed for fusion and exocytosis of the neurotransmitter vesicles, although the time for transmitter diffusion and post-synaptic channel activation is negligible.
ow is acetylcholine (ACh) inactivated after its release into the synaptic cleft?
After its release into the synaptic cleft, acetylcholine (ACh) is inactivated by being hydrolyzed by acetylcholinesterase (AChE). Additionally, ACh can be actively pumped back into the presynaptic terminal or diffuse away from the synapse.
What is the function of nicotinic ACh receptors in skeletal muscle end plates?
Nicotinic ACh receptors, activated by nicotine and inhibited by curare, have binding sites for ACh and chemically gated ion channels. When ACh binds, it makes the channel permeable to Na+ and K+, leading to cell depolarization and action potential propagation.
What is the role of neurotransmitters in chemical synapses across the nervous system?
Neurotransmitters are the mechanism of communication in chemical synapses, facilitating communication in all parts of the nervous system
What are the effects of an imbalance between excitatory and inhibitory neurotransmitters?
an excess of inhibitory neurotransmitters can produce predictable symptoms of over-inhibition, while an excess of excitatory neurotransmitters can lead to symptoms of over-excitation. Some neurotransmitters can function as both excitatory and inhibitory depending on the context.
Name two neurotransmitters that are both excitatory and inhibitory.
Norepinephrine (primarily excitatory but inhibitory in some brain areas)
serotonin (excitatory in the raphe nuclei; inhibitory in the cerebral cortex).
List some major inhibitory neurotransmitters and their effects.
DEGABA
Dopamine
Enkephalins
Gamma-aminobutryic Acid GABA
glycine, endorphins, dinorphins
What are some major excitatory neurotransmitters and their effects?
GASP!
Glutamate-most abundant excitatory neurotransmitter in the brain
Acetylcholine (AcH)
Substance P = pain
How does an excitatory post-synaptic potential (EPSP) contribute to the initiation of an action potential?
An EPSP must depolarize the membrane to the threshold level for an action potential to be initiated. It is a cumulative effect of excitatory signals.
What is the impact of inhibitory post-synaptic potentials (IPSPs) on action potential initiation?
IPSPs hyperpolarize the membrane, reducing the magnitude of the EPSP and decreasing the chance of reaching the action potential threshold.
What are the three types of sensory neurons and their general functions?
General Somatic Afferent (GSA): Widespread branches throughout the body; alert the CNS to pain, touch, and temperature; primary fast response includes withdrawal.
Special Somatic Afferent (SSA): Found in muscles, tendons, and joints; senses position and movement; important for body awareness.
General Visceral Afferent (GVA): Fewer and more limited distribution; receptors are on visceral organs; senses fullness and discomfort; pain is diffuse and unlocalized.
How do General Somatic Afferent neurons function and what do they detect?
General Somatic Afferent neurons have widespread branches throughout the body and detect pain, touch, and temperature. They alert the CNS to potential danger and initiate a primary fast response, such as withdrawal.
What is the role of Special Somatic Afferent neurons and where are they located?
Special Somatic Afferent neurons are located in muscles, tendons, and joints, and they sense the position and movement of body parts, aiding in body awareness and proprioception.
Describe the function and challenges associated with General Visceral Afferent neurons.
General Visceral Afferent neurons are located on visceral organs and are less precise compared to general somatic afferents.
They sense fullness and discomfort, and the pain is diffuse and hard to localize, making it difficult to pinpoint the exact source of discomfort or pain.
What is the primary function of the sensory unit (first-order neurons)?
The sensory unit perceives and conducts information about
stimulus discrimination,
tactile discrimination,
thermal sensation,
and position sensation via the dorsal root ganglia.
What are the three types of fibers in the dorsal root ganglia and their functions?
Type A Fibers: Largest, myelinated, fastest; conduct touch, temperature, pain, and pressure.
Type B Fibers: Conduct mechanical pain from subcutaneous structures.
Type C Fibers: Unmyelinated, small diameter, slower; conduct temperature, mechanical, and chemical pain.
What are the two main ascending pathways for sensory information and their primary functions?
Dorsal Column-Medial Lemniscal Pathway: Discriminative touch, precise localization, and stereognosis using three neurons.
Anterolateral Pathway: Crude touch, pain, and temperature sensations, with subdivisions including:
what are the 2 subdivisons of the anterolateral pathway, and where do they terminate ?
Paleospinothalamic Tract: Poorly localized, involved in chronic pain and autonomic responses.
-fibers terminate prior to thalamus
Neospinothalamic Tract: Well-localized, provides information about stimulus localization.
-terminate in the thalamus
